Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

288
FXUS63 KLOT 231155
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
655 AM CDT Sat May 23 2026

.KEY MESSAGES...

- Widely scattered showers and isolated storms are possible
  this evening through early Sunday afternoon (30-40% chance).

- Above normal temperatures are expected through early next
  week.

&&

.DISCUSSION...
Issued at 226 AM CDT Sat May 23 2026

A surface low analyzed over southeastern Indiana is gradually
moving northeastward toward southeastern Michigan and western
Lake Erie. Moisture wrapping around the northern edge of the
cyclonic flow is providing rain showers in northern Indiana.
Meanwhile, bands of showers along the far outer edge are moving
west over Lake Michigan toward Illinois. Coverage of showers
through mid morning should be confined to counties adjacent to
Lake Michigan, mostly isolated, and rain totals are expected to
be a trace to locally a hundredth or two. Modeled instability is
meager at best. So while the chance of lightning is "non-zero",
it is not expected. As the surface low continues its eastward
trajectory, showers will also move east over Michigan for drier
conditions by mid morning. Winds are expected to be light and
northerly before a lake breeze develops in the afternoon. High
temperatures for inland areas are expected in the 70s, but the
aforementioned lake breeze should limit heating near the lake
shoreline to the 60s.

An upper level trough over the Central Plains will move east
toward the western Great Lakes this evening through tomorrow,
driving a surface front from west to east across the forecast
area. Widely scattered showers out ahead of the front are
expected to arrive near the west border of the forecast area
early this evening. Model soundings show weak instability with
these showers that could lead to an isolated thunderstorm. But
the better instability, and better forcing in general, is
expected farther west along the front which should not arrive
until after sunset. After sunrise, instability will increase
renewing the chances (20 percent) for thunder along and ahead
of the front. There is some model disagreement on the exact
placement of the front after sunrise, but the highest confidence
in thunder development on Sunday is east of Interstate 55.
Current guidance has the front exiting the area to the east
during the afternoon with quieter conditions in its wake.

An upper level ridge is expected to grow Sunday night into
Monday. As surface high pressure slides over central Illinois,
southerly flow will advect a warmer air mass over the area.
Temperatures are expected to climb above normal into the 80s
both Monday and Tuesday.

Models are suggesting a 700 mb wave is expected to move
northward out of Texas Tuesday night before phasing with a
longer wave over the Intermountain west late in the week. The
expectation is that this wave would send a front over the
forecast area from south to north and provide another chance
for rain Tuesday night into Wednesday. However, at this range
there is still model disagreement on the progression of this
wave as well as how it phases late in the week (potentially
setting up a stagnant pattern) leading to low end PoPs through
the end of the week, mainly south of Interstate 80. Persistent
northeast winds late in the week are expected to help return
high temperatures back to seasonal norms.

DK

&&

.AVIATION /12Z TAFS THROUGH 18Z SUNDAY/...
Issued at 655 AM CDT Sat May 23 2026

Key aviation forecast messages:

- A period of IFR CIGs through mid morning near Lake Michigan.

- Light northerly winds turning east behind a lake breeze this
  afternoon at ORD/MDW.

- Another round of showers possible this evening near RFD and
  late tonight into the Chicago area terminals (30% chance).

After holding off all night the IFR stratus has made an inland
surge into ORD and MDW this morning which may linger through
~14-15Z before gradually lifting and scattering through midday.

Winds will be generally light north northeast near the lake
early this morning then becoming light northerly to potentially
variable through midday before a lake breeze turns winds
easterly in the afternoon. Farther west near RFD prevailing
light and variable winds will turn southwest to west late in the
afternoon ahead of a potential line of gusty showers. Have
introduced a PROB30 for these showers at RFD which are expected
to then decrease in coverage with eastward extent toward
Chicago.

Additional showers may develop near and ahead of an approaching
cold front late tonight into early Saturday morning. Have
introduced PROB30s for -SHRA at the Chicago area terminals to
account for this. While lightning can`t be ruled out with this
activity the potential is too low to include with this update
(20% chance).

Petr

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

Visit us at weather.gov/chicago